The present invention relates to the field of protective and/or decorative surface treatment of articles, particularly metals, plastics, and the like.
The present invention comprises novel derivatives of polyphenol compounds useful in the treatment of the surface of metal articles. The present invention also encompasses novel surface treatment solutions or dispersions, and methods of using these solutions or dispersions.
In accordance with the present invention, novel compositions, solutions and dispersions, and methods are provided for use in providing a protective or decorative metal surface treatment; these include the treatment of previously untreated bare metal surfaces, the post-treatment of phosphatized or conversion coated metal surfaces, the application of a paint or other decorative coating or film, and the like. The present invention additionally includes compositions and methods that are particularly useful for treating various metal surfaces including aluminum, steel and zinc metal surfaces. The compositions, solutions and dispersions, and methods of the present invention provide a coating on the metal surface which is effective in enhancing the corrosion resistance and paint adhesion characteristics of the metal surface whether previously conversion coated or not. A further and more detailed understanding of this invention can be obtained from the following disclosure. All parts and percentages are by weight unless otherwise indicated.
The need for applying protective coatings to metal surfaces for improved corrosion resistance and paint adhesion characteristics is well known in the metal finishing art as well as in other metal arts. Traditionally, metal surfaces are treated with chemicals which form a metal phosphate and/or metal oxide conversion coating on the metal surface to improve the corrosion resistance and paint adhesion thereof. The conversion coated metal surfaces are also generally rinsed or post-treated with a solution containing a hexavalent chromium compound for even greater corrosion resistance and paint adhesion.
Because of the toxic nature of hexavalent chromium, expensive wastewater treatment equipment must be employed to remove the residual chromates from plant effluent to comply with environmental regulations and to improve the quality of rivers, streams, and drinking water sources. Hence, although the corrosion resistance and paint adhesion characteristics of conversion coated metal surfaces can be enhanced by an after-treatment solution containing hexavalent chromium, these disadvantages in recent years have lead to much research and development in an effort to uncover effective alternatives to the use of post-treatment solutions containing hexavalent chromium. One alternative to the use of hexavalent chromium involves the use of derivatives of polyphenol compounds such as poly-vinyl phenol. Suitable derivatives and suitable treatment solutions are disclosed in earlier U.S. Pat. Nos. 4,517,028, May 14, 1985; 4,376,000, Mar. 8, 1983 to Lindert; and 4,433,015, Feb. 21, 1984 to Lindert and 4,457,790, Jul. 3, 1984 to Lindert, et al.; all of which are expressly incorporated herein by reference. Also see the two commonly assigned applications entitled "Treatment And After-Treatment Of Metal With Carbohydrate-Modified Polyphenol Compounds", U.S. Ser. No. 128,673; and "Treatment and After-Treatment Of Metal With Amine Oxide-Containing Polyphenol Compounds", U.S. Ser. No. 128,756; both of which are expressly incorporated herein by reference.